A line table of a cooling hearth to be used in the conventional production of steel bar material is, as shown in FIG. 3, formed with a channel 501 by equilateral angles 500 for conveying products 200 therealong. However, there is a danger that the products 200 will jump out from the channels 501.
Therefore, a trough apparatus for 2 strand high speed rolling as shown in FIGS. 4 and 5 was proposed in Japanese Patent Publication 56-31165 to solve the above mentioned problem. As shown in FIG. 5, a fixed arm 300 is provided at its end with a fixed channel part 302 formed with a semi-circular channel 301. An opening-closing arm 310 is rotatable around a fulcrum 313 and is provided at its end with a moving channel part 312 formed with a similar semi-circular channel 311 in opposition to the channel 301. When the both channels 301, 311 are butted, a conveying trough 320 is formed as a passage 321 of cylindrical space As seen in FIG. 4, the conveying troughs 320 are disposed in parallel and obliquity over a cooling hearth 100, and the arms 310 are rotated around the fulcrums 313. When the opening-closing channels 311 and the fixed channels 302 are separated, the steel bars 200 drop to the cooling hearth 100. In order to let the products 200 drop into grooves 101, 102 of the cooling hearth 100 as demanded, there are provided lower chute plates 330 under the conveying troughes 320 so that the bar products 200 are directed by striking to the lower chutes 330.
A trough apparatus for 1 strand high speed rolling as shown in FIGS. 6 and 7 was proposed in Japanese Utility Model 53-17637. As shown in FIG. 7, an arm 340 projects laterally from a column 700. The arm 340 is provided at its end with a fixed channel part 342 having a semi-circular channel 341 facing downwardly. An opening-closing U-shaped arm 350 is rotatable around a fulcrum 353, and the arm 350 is provided at its end with a moving channel 352 having a semi-circular channel 351 facing upwardly toward the channel 341. When both channels 342, 352 are butted, a conveying trough 360 is formed as a passage 361 of cylindrical space. As seen in FIG. 6, the conveying troughs 360 are disposed upwardly of the cooling hearth 100, and the arms 350 are rotated around the fulcrums 353. When the channels 351 and the channels 341 are separated, the steel bars 200 roll on chuting plates 370 and along auxiliary guides 380, and drop onto the cooling hearth 200.
However, the first mentioned conveying trough apparatus was involved with the following problems:
(1) Due to thermal expansions in the channel parts 302, 312 at the ends of the fixed arm 300 and the opening-closing arm 310, a gap is caused in position as seen in FIGS. 8(a)(b) between the channels 301, 311, and the bar product 200 is injured by the edges of these gapped channels 301, 311.
(2) The products 200 must be conveyed to adjacent individual grooves 101, 102 of the cooling hearth 100, and each product 200 is directed by dropping it from a trough 320 so that it collides with a chute 320, and is conveyed to one of the grooves 101, 102. However, since the product has a length of over several tens of meters, it does not always drop evenly at the front and rear ends and the timing of collisions with the chute 320 vary among the parts of the product 200, thereby causing bending or twisting.
(3) If the bottom face of the conveying trough 320 has a V shape of moderate gradient (when the moving channel 312 is closed during movement of the products along the conveying trough 320) then, when a product 200 having an inferior rolled property (especially straight) is dropped, the product 200 is caught by the fixed channel 301, thereby causing bending or twisting.
The second-mentioned apparatus was involved with the following problems:
(4) The bar lengths 200 which have passed through the 2 strand concurrent rolling and have been cut into bar lengths are not dropped together, but a bar length 200 from one strand is held in a trough 360 (while a bar length 200 from the other strand is dropped into one of the grooves 101 or 102 of the cooling hearth 100) by delaying the dropping timing. But in this case, since subsequent products 200 are sent continuously, a problem occurs about the time cycle. That is, the treating cycle per bar length to be sent to the cooling hearth 100 must be extended by the staying time in the trough; otherwise the arriving products 200 could not be conveyed in and out successively. Methods for extending the treating time per bar length include delaying the rolling speed and enlarging the product in length. However, the former would decrease productivity and the latter would cause trouble in bending the products 200 because the length of each bar length is enlarged, and inconveniences such as rising costs of facilities, buildings and others may be expected.
(5) The possibility of conveying two products 200 into one groove 101 or 102 of the cooling hearth 100 at the same time has been considered, but taking into consideration twisting or bending of the product, this method is out of questions. As shown in FIGS. 9(a), (b), (c), the two products are twisted or bent within one groove 101 or 102.
The invention has been designed to solve the above mentioned problems, and to send the rolled products while keeping them straight, to minimize the dropping distance of the rolled products of the two strands into the groove, and to avoid twisting of the products by dropping.